Allergy is a disorder of the immune system, causes a lot of discomforts and can interfere with our day to day life. They are caused by seasonal changes, certain food, stress, pollution etc.
Ayurveda believe that an imbalance of three doshas can cause allergies. When your agni (digestive fire) becomes weak, it causes Ama (toxins) to get accumulated in the body and further weakens the immune system.